This invention relates generally to linear roller bearings and, more particularly, to linear roller bearings with adjustment devices for providing alignment, preload or clearance.
Manufacturing tolerance in linear roller bearing complements and/or the desired relationship to fixed surfaces that backup the bearing races require an adjustment capability after assembly to achieve a desired preload or clearance condition, as required for a particular application.
The accepted method for providing adjustment after assembly of the bearing complement uses adjustment screws that bear upon the bearing race, or upon the backup surface that supports the bearing race. This method requires extreme care that the load (or clearance) is uniform along the entire length of the bearing race. Furthermore, the bearing race or backup surface must be of substantial thickness to have sufficient stiffness to prevent disparities between the contact points of the adjustment screws. This method cannot be used in applications where the total package envelope does not allow for ample thickness of the bearing race or backup surface, or when there is inadequate accessibility for the adjustment screws.
When thickness limitations prevent the use of adjustment screws, as just described, selective assembly of components must be used to achieve the desired preload or clearance condition required. Selective assembly requires that multiple sizes of bearing races and/or multiple diameters of rolling elements are available during assembly. For high precision assemblies, this method is time consuming and costly, requiring careful measurement of each component in order to correctly match the bearing assembly. Furthermore, for economic and practical reasons, the variety of components is such that instances occur which fall between the combinations of components available, leading to an under- or over-loaded condition of the final assembly.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.
In one aspect of the invention, this is accomplished by providing a linear bearing comprising an elongated two-piece bearing race having two longitudinally extending side members. A plurality of rollers is positioned adjacent to the two-piece bearing race for rolling contact therewith, the rollers having a xe2x80x9cclearancexe2x80x9d with respect to the side members of the two-piece bearing race. A backup member supports the two-piece bearing race along the length of the side members, the backup member having angled surfaces such that ends of the rollers are closer to the angled surfaces than are intermediate portions of the roller. Spreading means is provided for spreading apart the two side members of the two-piece bearing race such that the angled surfaces of the backup member direct the side members of the two-piece bearing race toward the rollers to decrease the xe2x80x9cclearancexe2x80x9d with the rollers.
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures.